The Department for Business, Innovation and Skills (BIS) is responsible, with
the Office for National Statistics (ONS) for publishing the National Statistics
on trade union membership.

Estimates are presented for the proportion of people in employment who are trade
union members in both the United Kingdom and Great Britain, and for employees
whose pay and conditions are affected by collective agreements. We also provide
trade union densities by age, sex, ethnicity, income, full and part-time
employment, sector, nation and region.

The latest trade union membership publication contains annual estimates of trade
union densities for employees and all workers from the Labour Force Survey (LFS)
for the fourth quarter of 2009. Further information is available
here.